Interactivate

Histograms and Bar Graphs

Abstract

The goal of this lesson is to introduce histograms, bar graphs and the concept of class interval.
An activity and three discussions with supplemental exercises help students learn how data can be
graphically represented (and mis-represented). Students will learn to distinguish between bar
graphs and histograms and to use each in the appropriate situations.

Objectives

Upon completion of this lesson, students will:

have been introduced to histograms and bar graphs

have understood the difference between bar graphs and histograms

have seen examples of how data can be represented in a variety of graphical forms

Summarize, represent, and interpret data on a single count or measurement variable

Third Grade

Measurement and Data

Represent and interpret data.

Grades 6-8

Data Analysis and Probability

Formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them

Select and use appropriate statistical methods to analyze data

Grades 9-12

Data Analysis and Probability

Formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them

Grade 7

Number and Operations, Measurement, Geometry, Data Analysis and Probability, Algebra

COMPETENCY GOAL 4: The learner will understand and use graphs and data analysis.

Grade 8

Number and Operations, Measurement, Geometry, Data Analysis and Probability, Algebra

COMPETENCY GOAL 4: The learner will understand and use graphs and data analysis.

Introductory Mathematics

Algebra

COMPETENCY GOAL 4: The learner will understand and use graphs and data analysis.

Data Analysis and Probability

COMPETENCY GOAL 3: The learner will understand and use graphs and data analysis.

4th grade

Data Analysis and Probability

Standard 4-6: The student will demonstrate through the mathematical processes an understanding of the impact of data-collection methods, the appropriate graph for categorical or numerical data, and the analysis of possible outcomes for a simple event.

6th Grade

Data Analysis and Probability

The student will demonstrate through the mathematical processes an understanding of the relationships within one population or sample.

3rd Grade

Probability and Statistics

3.22 The student will read and interpret data represented in line plots, bar graphs, and picture graphs and write a sentence analyzing the data.

5th Grade

Probability and Statistics

5.17c The student will create a problem statement involving probability and based on information from a given problem situation. Students will not be required to solve the created problem statement.

7th Grade

Probability and Statistics

7.16 The student will create and solve problems involving the measures of central tendency (mean, median, mode) and the range of a set of data.

7.17 The student, given a problem situation, will collect, analyze, display, and interpret data, using a variety of graphical methods, including frequency distributions; line plots; histograms; stem-and-leaf plots; box-and-whisker plots; and scattergrams.

7.17 The student, given a problem situation, will collect, analyze, display, and interpret data, using a variety of graphical methods, including

8th Grade

Computation and Estimation

8.3 The student will solve practical problems involving rational numbers, percents, ratios, and proportions. Problems will be of varying complexities and will involve real-life data, such as finding a discount and discount prices and balancing a checkbook.

8.3 The student will solve practical problems involving rational numbers, percents, ratios, and proportions. Problems will be of varying complexities and will involve real-life data,

Patterns, Functions, and Algebra

8.17 The student will create and solve problems, using proportions, formulas, and functions.

8.18 The student will use the following algebraic terms appropriately: domain, range, independent variable, and dependent variable.

8.18 The student will use the following algebraic terms appropriately: domain, range,

Probability and Statistics

8.12 The student will make comparisons, predictions, and inferences, using information displayed in frequency distributions; box-and-whisker plots; scattergrams; line, bar, circle, and picture graphs; and histograms.

8.12 The student will make comparisons, predictions, and inferences, using information

Textbooks Aligned:

Reason for Alignment: This lesson shows uses for each, and a discussion of when to use each type of graph. This should be easily understood by students at this level. There are data sets included for practice and analysis.

Reason for Alignment:
This lesson should help students sort out the differences between bar graphs and histograms and help them understand their specialized uses. There is a good discussion suggested for this. This lesson should also help students as they use their own data for each of these types of data displays.

Student Prerequisites

Geometric: Students must be able to:

recognize how data can be plotted and interpreted from shapes such as bar graphs

Key Terms

bar graph

A diagram showing a system of connections or interrelations between two or more things by using bars

class interval

In plotting a histogram, one starts by dividing the range of all values into non-overlapping intervals, called class intervals, in such a way that every piece of data is contained in some class interval

histogram

A bar graph such that the area over each class interval is proportional to the relative frequency of data within this interval

Lesson Outline

Focus and Review

Remind students of what they have learned in previous lessons that will be pertinent to this
lesson and/or have them begin to think about the words and ideas of this lesson:

What are some different ways to represent data?

Is there one way that is superior to all the others?

Objectives

Let the students know what they will be doing and learning today. Say something like this:

Today, class, we are going to learn about the differences between bar graphs and histograms.

We are going to use the computers to learn about the differences between bar graphs and
histograms, but please do not turn your computers on until I ask you to. I want to show you a
little about these activities first.

Teacher Input

Use the
Bar Graph activity to familiarize students with visually representing data. Be sure to demonstrate the
importance of vertical scale in bar graphs.

Use the
Histogram activity to demonstrate the importance of class interval size and vertical scale in
histograms.

Guided Practice

Lead a class discussion about
Class Intervals to deepen and formalize students' intuitive understanding of histograms, bar graphs, and
class intervals. Use
Sample Problems on Bar Graph Scales to provide examples for the discussion. Students can read the sample problems and try to
solve them individually or in groups, or use them as examples and create their own statistics
problems for themselves and/or for other students.

Next, initiate a discussion based on
Vertical Scale to enhance the students' understanding of how data can be represented graphically.

You may wish to bring the class back together for a discussion of the findings. Once the
students have been allowed to share what they found, summarize the results of the lesson.

Alternate Outline

This lesson can be rearranged in several ways.

Instead of initiating class discussions, have the students read the discussions independently,
and then see how well they understood by having them complete the sample problems worksheets
that accompany each discussion.

For further investigation into the representation of data, and to practice working with
fractions and decimals, students can work with
Sample Problems on Data Abuse.

Suggested Follow-Up

After the discussions and activities, the students will have seen examples of bar graphs and
histograms, and be able to tell them apart and know the circumstances when each should be used.
The next lesson,
The Bell Curve, covers the normal distribution and the bell curve controversy.